1. Field of the Invention
The present invention relates to an optical proximity effect correcting method and a mask data forming method in a semiconductor manufacturing process.
2. Description of the Related Art
In an optical lithography process of a semiconductor device manufacturing process, an optical proximity effect is incurred. The optical proximity effect implies that exposure transcription cannot be carried out accurately in the same shape due to light interference between proximity lights adjacent to each other. Therefore, it is required to reduce pattern dimension error caused by such optical proximity effect. The reduction of the pattern dimension error is compensated by correcting the proximity effect, as known in Japanese Laid Open Patent Application (JP-A-Heisei 5-80486). This correction technique is the calculation technique of modifying a line width of a correction target pattern through calculation, as known in Japanese Patent Publication 2616467.
As a technique of correcting the proximity effect, a technique disclosed by Oberdan W. Otto et al, entitled [Optical/Laser Microlithography VII, Vol. 2197, SPIE Symposium on Microlithography 1994], pages 1-16, in a name of [Automated optical proximity correction—a rules—based approach] is well known.
In an actual pattern design, there are various sizes (wiring widths) of design patterns, and there are also various space widths and position relations between the design patterns. Here, the combination of a wiring pattern and a contact pattern makes its pattern shape further variable.
If the proximity effect is corrected under such situation, there may be a case that the sufficient proximity effect correction cannot be attained only by adding a correcting pattern having a certain shape to each of the various design patterns. In this case, it may be considered to limit a design rule so that there is no occurrence of the insufficient correction after the addition of the correcting pattern having the certain shape. However, a method of limiting a design rule and a method of validating a design method are not still established. Also, such limitation and validation may result in a drop of design efficiency and largely increase validation process time.
Japanese Laid Open Patent Application (JP-A-Heisei 10-69058) discloses the following technique with regard to an optical proximity correcting method. Not only the optical proximity correction is limited to electrically related structure, but also the individual shape edges are processed. Thus, accuracy of the correction is improved, and also the occurrence of irregularity in design is avoided to thereby reduce the influence on mask manufacture to a minimum. An important edge area in the electrical related structure is analyzed, sorted and processed to thereby receive the optical proximity correction.
Japanese Laid Open Patent Application (JP-A-Heisei 8-321450) discloses the following technique with regard to a mask pattern correcting method. In a mask pattern correcting method for a photo mask used when a pattern is projected to and exposed on a substrate, if a first mask pattern and a second mask pattern adjacent to each other under a certain distance are formed on the photo mask, a pattern correction data is generated by using a shift amount induced at a time of exposing the first mask pattern and the second mask pattern on the substrate and a shift amount induced at a time of etching. Then, a side of the first mask pattern is moved in accordance with a correction amount corresponding to a distance between the first and second mask patterns.
Japanese Laid Open Patent Application (JP-A-Heisei 10-239826) discloses the following technique with regard to a photo mask pattern designing apparatus. It is provided with: a pattern condition input device used for an input of a pattern design rule which implies a condition to extract a photo mask pattern portion to be optimized in a usual photo mask pattern; a pattern extracting device for extracting a pattern cell before the correction of an optical proximity effect, which does not meet the pattern design rule and on which the optical proximity effect correction should be performed; an optical strength simulator for repeatedly performing an optical strength simulation on a pre-optimization pattern cell for a plurality of times; and a pattern optimizing device for optimizing the pattern cell before the correction of the optical proximity effect, in accordance with the plurality of simulation results.
Japanese Laid Open Patent Application (JP-A-Heisei 2-189913) discloses the following technique with regard to a method of forming a pattern of a semiconductor device. This method of forming the pattern comprises: a step of preliminarily forming the patterns by using the elements in which mask patterns where proximity effects occur are formed in advance in various dimensions, when forming the patterns of a semiconductor device by using a mask containing a mask pattern where the proximity effect occurs and a mask pattern where the proximity effect does not occur; a step of determining a relation between the dimensions of these masks and the actually-measured dimensions of the formed patterns; and a step of determining a mask dimension corresponding to a pattern dimension required from the determined relation and accordingly correcting the dimension of the mask pattern in accordance with a difference between both the pattern dimensions.
Japanese Laid Open Patent Application (JP-A-Heisei 10-104818) discloses the following technique with regard to an optical proximity effect correcting method. This method determines an area rate judgment standard as to whether or not it is necessary to correct an optical proximity effect and a judgment distance which receives the influence of the optical proximity effect from another exposure point of an exposure point on the basis of an optical condition in an exposing apparatus in which a photo mask is mounted. This method divides each side of a photo mask pattern into division sides, each equal to or less than a preset length. This method determines an area rate occupied by the photo mask pattern in which a radius centered at a middle point on each division side belongs to a circle of the judgment distance, for each division side. Then, this method compares the area rate of each division side with the area rate judgment standard, and accordingly judges whether or not it is necessary to correct the optical proximity effect for each division side.